Did you check to see if this excursion was cancelled? If it’s still showing, that you can book it, then it could be a website issue.
They usually email your TA or whomever booked it, but not always, if it has been cancelled.
The only source I know, is the phone tree, regular phone line and pick the option to book an excursion. They could pass on your problem to the customer solutions desk to correct.
Does it show in your Travel Summary?
Let us know if those phone numbers worked that
@Rick&Jeannie gave you.
Would be very helpful.